1. Field of Invention
The present invention relates to the field of tubular reflecting. More particularly, the present invention relates to a tubular reflector and a tubular lighting device for automotive lighting.
2. Background of the Invention
There is generally an increasing need, particularly in the automotive lighting industry, for tubular light source applications. For example, one such application may be to a Center High Mount Stop Lamp (i.e., CHMSL). Tubular light sources used in such applications may be mounted within an elongated reflector having a parabolically shaped reflecting surface. For example, FIG. 1 illustrates a tubular lighting device 5 having a height y and having a tubular light source 10 situated within a parabolic reflector 20. The reflector 20 has a first aperture end 26 and a second aperture end 28, the distance between the two ends 26, 28 (i.e., distance y) defines a reflector aperture 35.
Reflector 20 includes a parabolically shaped reflective surface 24 for reflecting rays emitted from source 10. Surface 24 extends from the first reflector end 26 internally within reflector 20 to the second reflector end 28.
Generally, the light source 10 is disposed near a focal point, f, of the parabolic reflector 20. In this manner, light emanating from light source 10 is distributed away from source 10 and towards reflecting surface 24. Light incident upon reflecting surface 24 is reflected and directed forward towards aperture 35, parallel to a paraboloid axis of reflector 20, axis-a. Aperture 35 may include a lens 36 through which the reflected light is then transmitted. For example, the lens may or may not have pillow or fluting optics. These optics may serve to provide additional spread if necessary, depending upon the desired beam pattern. The lens optics may also serve to provide certain aesthetic characteristics of the reflector, such as providing a more uniform appearance.
For example, light ray 14′ emitted from source 10 is directed towards the reflective surface 24 of reflector 20. Ray 14′ is incident upon surface 24 at point R1 and ray 14″ is redirected towards aperture 35 parallel to axis-a. In a similar manner, emitted ray 16′ is directed towards reflector surface 24. Ray 16′ is incident at point R2 and ray 16″ is redirected towards aperture 35, parallel along axis a. At aperture 35, rays 14″, 16″ may be refracted by a prism or lenses of the lens 36. In this manner, reflector 20 may be used in conjunction with a lens device to form a lighting device, forming a desired beam pattern.
One disadvantage of tubular lighting devices, such as device 5, is that, because of the location of the light source, the amount of controlled light (i.e., light directed to the aperture) may not be optimized because of the location of the light source. Consequently, the overall illumination efficiency of the lighting device may be adversely affected. One reason that efficiency may be adversely affected is that a reflector has a relatively large height in comparison to the depth of the reflector. So, the amount of light that may be collected by the reflector and that forms the desired beam pattern is small. For example, as shown in FIG. 1, α1 represents an upper half amount of light emanated from source 10 and reflected towards aperture 35. Reduced efficiency and therefore a smaller α1 may be caused in part by emanated light that is not redirected towards lens 36 and therefore does not contribute to the overall efficiency.
For tubular reflectors having relatively small apertures, light emanating from a light source, reflected by the reflector, and hence directed towards the reflector aperture is limited. Since certain tubular reflector applications require a small aperture, such as the aperture in an automotive CHMSL application, emanated light may not be reflected and/or directed towards the aperture. Consequently, a portion of the overall illuminated light does not enhance the overall efficiency of the reflector, and therefore the efficiency of overall lighting device.
Another general disadvantage of parabolic reflectors, such as reflector 20 shown in FIG. 1, is the restricted height of a tubular light source 10. Typically, in certain automotive lighting device applications, such light sources may range in height (diameter) from 3 mm to 10 mm. The light source height may be limited by design constraints imposed by certain applications, particularly automotive lighting design constraints.
The reduction of the overall height for styling and mounting requirements may also result in limiting reflector efficiency. To a certain degree, the reduced height may be offset by increased depth, but only with diminishing effects on the light efficiency. For example, where the light source is mounted in an automobile spoiler, a limiting design constraint may be the overall dimensions of the spoiler. Usually, a limiting constraint is the neon tube system. While it may be possible to use a neon tube having the length of a spoiler, using a tube having such a length may be impractical due to certain power considerations.
There is, therefore, a general need for a tubular light source and a tubular reflector that increases the collection of emanated light such that an increased amount of reflected light may be directed towards the reflector aperture. There is also a general need to increase the amount of reflected light, direct this collected light in a desired beam pattern while also increasing styling flexibility. A need also exists for a reflector configuration that increases the collected and emanated light while also attempting to limit the overall height of the tubular reflector.
A need also exists such that a resulting illumination distribution pattern may satisfy certain automotive illumination requirements, such as a Federal Motor Vehicle Safety Standards 571.108 (“FMVSS”). FMVSS which is herein entirely incorporated by reference and to which the reader is directed to for further information.
Alternatively, there is a general need for a reflector configuration that increases the collected and emanated light such that a resulting illumination distribution pattern may satisfy certain lighting standards imposed by automotive manufacture, such as Ford, General Motors, Honda or the like.